In the end, John ended up sleeping in the fifth years' dorm, because, after all, a teenager, sharing a dorm with eleven-year olds?
Throughout the next days, John learned many things. He learned to shut his mouth when faced with the Ravenclaw riddle-me-this, and to keep it shut until, and when, Sherlock would pipe up with the answer. He learned to stop panicking when he couldn't find a lid for his quill. He learned to skip the forty-secondth staircase, and stopped having to call for someone to pull him up from the gap he would suddenly find himself trapped in.
His classmates were all questions, painfully obvious in their attempts to casually bring it up. John replied the best he could—which was, unfortunately, not very good. "I don't know," made up ninety percent of his answers.
The students would then grumble with annoyance and pester him some more, but soon realised John's guess really was as good as theirs, and eventually, John found himself entering the common room and not immediately being cornered by students.
Anyways, they had more important things on their mind. To be specific, the "owls", as Mike had called them.
He had then gone on to explain just how hard it was going to be, and how everyone had started studying already, etc, etc.
John made a face. Just his luck.
Speaking of which: John frequently borrowed Sherlock's owl ("Jackson. Most random, unoriginal name I've ever heard. Won't respond to anything else. Anything! Sodding stubborn owl.") to write to his parents, and soon found that Sherlock was right—the owl did like him. It hooted whenever it caught sight of John, and, although it still sent food attacking, Jackson always allowed John to tie his letters without complaint.
His parents were still quite overwhelmed, as was John, but, eventually, and with lots of inside jokes tests (to make sure it wasn't a kidnapper just pretending to be John) they'd grown to trust. Nevertheless they still pestered John with constant questions, naggings, and fusses, once owl-ing him a fully-packed lunch, complete with a juice box and a Thermos. The owl was not pleased.
So, things sorted themselves out, and, eventually, John could finally start to concentrate on his classes, and, thankfully, begin to catch up, if only a little, on four years of missed magic education.
John didn't care how hard it was; he absolutely refused being in a class with first-years. Anderson, upon being told this, shrugged, jotted something down, and waved him away with a small slip of paper: a schedule, a mash of different classes. "Assuming you don't know the subjects very well," Anderson had said, and John nodded gratefully, scanning the paper, which he was pretty fine with.
That was how he ended up being in random classes, mostly with fifth-years, but just a bit with fourth, and thirds—John didn't really mind them, actually; they sort of just shrugged it off, upon seeing his entry.
Sherlock, Molly, and Mike were with him in some of their classes, but apparently Sherlock Holmes had carte blanche to the school, because he somehow found a way to attend one of John's forth-year's. And no one complained, or even brought it up, when they noticed the older, dark-haired boy sitting with the usual sixth-year student. Strange, but John was too grateful to question it.
After a couple days, Anderson approached John once again, and (perhaps a bit sheepishly) apologised for waving John away so fast. He explained that this has never happened before, and that, if the need arise, John could have himself a tutor, or some after-school extra lessons. "You could do the O.W.L's later, if you wish."
After sleeping on it, John decided to, in fact, not have a tutor for now, and actually do the O.W.L's at the same time as the other fifth years. Maybe it was his Gryffindor showing, but John wanted to see how much he could catch up on, without any special aid from teachers. (Although, Sherlock was basically a tutor himself, he noted with amusement.)
He could always tell Anderson he changed his mind if he really needed to, though he hoped he wouldn't.
John studied hard. He read up on books. He paid attention in class. He even attempted to use his phone, but the connection was down—guess you can't have the best of two worlds.
He ended up, actually, pretty decent at most subjects. Which would be great, better than that, if it weren't for the fact that, more often than not, John would attempt a levitation for hours without success, only to have Sherlock pop up and do it for him in less than ten seconds. Similar scenes occurred in most other subjects as well.
Except for one.
Sherlock despised Astronomy.
He just couldn't understand it. The planets, the movement, the stars and the whatever; it all just seemed to be an entire waste to him.
"Why does any of it matter? Whether the Earth goes around the sun, or if the moon around Earth; if everything went around everything it wouldn't make a penny's worth to me, or my work."
"Funny; you tend to think the world rotates around you," John murmured, trying to make the telescope show something other than his eyelashes.
"Ah," said Sherlock, quietly. "Good point."
Either way, none of the teachers liked him very much. Scared, vaguely amused, embarrassed, annoyed, mortified, it all came together in a big Sherlockian bundle—the downside of being scarily observant and having the urge to point out humiliating facts whenever they were spotted—in other words, all the time.
John wasn't one to make friends easily, he never was, but he was happy to say being a late wizard did not completely obliterate his chances of making any.
Even though, as quoted from Mike: "What does it mean, when the easiest friends you make are with Sherlock Holmes and a ghost?"
Mike was, in the least, surprised, or even awed, to find John capable of amiable chatter with Sherlock. "Most people can't stand being with him in the same room."
John had laughed, and shrugged it off.
However, John thought, he did have an enemy.
The Gryffindor who had cornered John the other day never did it again, only sending furious, but with underlying fear, glares towards him whenever possible. John couldn't help but feel more than a little curious (and frightened) as to what Sherlock did, but whenever he brought the topic up Sherlock would shrug, or wink, or give a infuriatingly vague explanation, and John eventually gave up and asked his Headmaster, who paled upon the subject and told it in a nervous whisper: apparently that had been his first bully—he had lost control of himself and, in his fury, cast a body-bind spell on the poor Gryffindor, who John learned was Charles, and thrown him out the window.
It had been both his first, and his last.
John was wary of windows for quite a while after—Sherlock grinned crookedly and made some comment on teaching John the body-binding spells.
One day, during what they called "extra-practise", John gritted his teeth and glared at his wand, as he attempted to float his spell book (open to the hovering-charm page and flat on the ground), for what must've been the millionth time. He tried again and again, to no avail, and John couldn't help but wonder when he would be good enough to set it on fire.
They were in a large, empty room, originally dusty but now cleared away from John's constant entering. Sherlock had showed it to John one day, another one of his secret passages. John wasn't sure if magic was allowed there, but didn't really care—he wasn't doing anything bad.
After a couple more attempts, Sherlock held up a hand, cast a sound-proof charm, and gestured John to continue.
This time. This time, for sure. John steeled himself and jabbed the wand at the spell book.
"WINGARDIUM LEVIOSA!" he screamed, voice cracking . The book remained on the floor, and John could hear Sherlock's partially held-in laughter.
"No, no, no," he said, giggling. "You're holding your wand way too tight. Relax a bit and loosen your grip. Now try again."
John felt his face heat up. Nevertheless, he did as Sherlock said.
"And it doesn't matter how loudly you recite it," Sherlock added. "You could whisper and it still wouldn't work."
"Thanks," John grumbled, and tried again, quieter, swish-and-flicking his wand.
"No!" Sherlock barked out, and John flinched. Sherlock shut his eyes, tightly, and slowly let out a breath, before speaking again, softer. "You're holding your wand like a pencil," he rushed out. John adjusted his grip and held it even more like a pencil.
"Just—oh, no," Sherlock distressed, as John nearly snapped his wand in an attempt to straighten his fingers.
"Here."
Sherlock stepped closer, reached over, took John's fingers, and moved them to the correct position, all the while not meeting John's eyes. "There."
John mumbled a thanks, highly conscious of how warm Sherlock's hands were, and tried again.
"Wingardium Leviosa!"
The spell book shot up. It hovered in mid-air, as if tied by an invisible string. John sucked in a breath and stared, accidentally letting his wand drop to his side; the book fell down with a dull thump. But John wasn't aware of this, as he spun around and turned to Sherlock.
"Did you see that?! I did it!" he said, smiling brightly, happy and hyper.
Sherlock smiled, a little proudly. "Nice job," he said simply, and John beamed.
His magic steadily improved thereafter, and although he wasn't nearly as good as any of the others, he was still "not too shabby for a 'first-year'," and John felt that was good enough for now.
One october morning, John woke, checked his schedule, and, with a pang of panic, exhilaration, and anticipation, realised it was going to be their first flying lesson.
John was incredibly wary of this, especially since this one was with wizards his age, and it only increased as he eyed the tattered, ratty old broomstick they bought in Diagon Alley, that looked like it couldn't even sweep up a pile of dust without shattering.
"Don't worry if nothing happens," Sherlock had told John, during breakfast. "It didn't for me."
"For how long?" John had asked, piqued, and Sherlock responded by silently pouting into his oatmeal. John struggled to keep his smile under control.
"Now, on three, I want you all to shout 'up'!" the professor's voice jolted John from his thoughts. He looked at his trembling hand, hovering over the broom. He steadied it as well as he could, and swallowed, killing the butterflies in his stomach.
"UP!"
John's broom flew up immediately, fitting comfortably into his palm. He was so surprised he let out a small squeal, and then smiled sheepishly at the giggling classmates beside him. It was only a recap of sorts, and everyone had done it, but that didn't stop John from beaming with pride—first time, and, most of all, better than Sherlock!
"Kick off firmly with your feet," instructed the professor. "Keep your balance and don't take your eyes off the front."
John looked around frantically. Flying? Already?
The other students apparently seemed quite nonchalant, and so John swallowed, killed the now-zombie butterflies in his stomach, and gritted his teeth, keeping a firm but loose hold on the stick, just as instructed.
"One, two, three—GO!"
John kicked his feet, hard, shutting his eyes. He gasped, tightened his hand, and then he felt the wind whip his hair and he heard the wind whistle around his ears and then he opened his eyes and he was flying.
A laugh bubbled out of him, a giddy, delighted laugh. It was absolutely wonderful. He pulled at the broom, gently, and turned around to meet dozens of smiling faces all around him.
"Nice job," commented the professor, who had, also, kicked off, and who was now hovering in front of the students. "And a very well done job to Mr. Watson here, first-time flyer!"
John beamed with pride. Oh, Sherlock is going to flip.
Broomstick use wasn't allowed outside of lessons, so John had to wait, agonisingly, until the day when they shared classes. Flying seemed to just came to him naturally (unlike most of the other subjects) and he improved with each passing day, until he was average, perhaps even better, than some students.
When the day finally came John confidently flew up, swooped around, and hovered about a metre up in the air. He looked over at Sherlock, whose broom flew up—and promptly smacked him in the face.
"Finally, something I'm better than you at," John remarked. Sherlock rolled his eyes with a scowl as he glared at the broomstick with the expression of a man who wasn't used to being amazing at everything, and absolutely hated it.
Sherlock tried again, and this time, he managed to wobble in the air, at the same height as John, for about ten seconds, until it tilted dramatically and Sherlock let out an exasperated noise, before he gracefully and easily jumped off the broomstick and landed on the ground with barely a thump. John was delighted.
But, of course, Sherlock always had to have his revenge, and it seems as though he decided that, this time, the way for this was to constantly pester John about trying out for Quidditch.
"It's quite simple, really," he encouraged, as they walked down the hallway together, and as they passed the Quidditch Cup and John simply glanced at it, and as Sherlock decided to take that as a reason to launch into his well-rehearsed speech, once again.
"Then do it with me!" John said back, his usual response to this speech.
Obviously John wanted to get in. It was a mish-mash of sports, while flying, on broomsticks—what could possibly be better? But one look at the sign-up sheet made him reconsider. There weren't much people he knew, and even less of the ones he was relatively friendly with. Even worse, the Gryffindor had marched up, shoved John aside, and scribbled his name on the list with a nasty grin.
They turned a corner as Sherlock spoke again. This was usually the time he would roll his eyes with a "John, you know I'd make a fool of myself" and John would say, "Oh, and God forbid that!" and Sherlock would smirk and then they would move on.
But not this time.
"Alright," said Sherlock, so naturally John walked on for a full three seconds, almost saying his usual response, before his mind processed, and when it finally did he ran smack into a wall.
John glowered and winced as Sherlock burst into a fit of giggles. Sherlock looked around before drawing out his wand and quickly healing the bruise with a quick mutter.
John turned to Sherlock. "What, you're serious?"
Sherlock shrugged. "Why not? It's not like I'll get in anyways."
John wondered why Sherlock seemed to either completely veto something, or be utterly nonchalant about it, but didn't question it. He found he couldn't ever really question anything Sherlock said, or did.
"Promise?" he asked dubiously.
"Nah," said Sherlock, breaking off in a run.
After John's indignant cry, and after a sprint chase down a hallway and apologies to many professors, John caught Sherlock, who was lazing by the Slytherin common room entrance, by the shoulder, and turned him around.
"Come on," he said. "Just try out with me. What's the worst that can happen?"
SB has pointed out the issue with the classes, and, frankly, I'm quite embarrassed to say it's been ages since I've re-read Harry Potter, and so I have no idea whatsoever of how the classes work/function. I've attempted to correct these plot holes to the best of my abilities, but please tell me if I've missed/messed up anything!
